Preheat your oven to 400°F and line a baking sheet with parchment paper.
Slice the eggplant into 1/2-inch thick rounds, brush lightly with olive oil, and roast for 20 minutes until tender.
While the eggplant roasts, heat a skillet over medium heat and brown the ground lamb with the diced onions and minced garlic.
Stir in the tomato puree, dried oregano, cinnamon, sea salt, and black pepper, then let the mixture simmer for 10 minutes to thicken.
In a small mixing bowl, whisk together the Greek yogurt, egg, and grated parmesan cheese until the mixture is smooth.
In a small oven-safe baking dish, layer half of the roasted eggplant, followed by the lamb mixture, and then the remaining eggplant.
Spread the yogurt bésamel evenly over the top layer and bake at 375°F for 20 to 25 minutes until the topping is set and lightly browned.